Silicon nitride microflower-nanowire double-layer composite thermal insulation aerogel paper and one-step preparation method thereof

Abstract

The invention discloses silicon nitride microflower-nanowire double-layer composite heat-insulating aerogel paper and a one-step preparation method thereof, and belongs to the technical field of heat-insulating and fire-resistant silicon nitride aerogel paper. The composite heat insulation aerogel paper comprises silicon nitride microflowers and silicon nitride nanowires, the silicon nitride microflowers grow on the surface, close to the airflow scouring side, of the silicon nitride nanowire; in a three-dimensional space, the silicon nitride nanowires are mutually crossed and interlocked, and the silicon nitride microflowers and the silicon nitride nanowires are interlocked. The composite heat-insulating aerogel paper can solve the technical problem that the service life of the material is affected due to the fact that the existing silicon nitride nano material is easily damaged after being burnt at 600 DEG C for a long time (more than 70 minutes).

Description

Technical Field

[0001] The invention belongs to the technical field of heat-insulating and fire-resistant silicon nitride aerogel paper, and specifically relates to a silicon nitride micron flower-nanowire double-layer composite heat-insulating aerogel paper and a one-step preparation method thereof. Background Art

[0002] One-dimensional silicon nitride nanomaterials have excellent properties such as good chemical stability, high temperature resistance, good flexibility, corrosion resistance, and good fire resistance. Silicon nitride nanomaterials have abundant micro-nano pores, which prolong the solid heat conduction path during heat transfer, block more air, make the phonon thermal vibration of air more intense, increase the heat consumption during heat transfer, and hinder heat transfer. However, in the process of preparing silicon nitride nanomaterials, the selection of raw material carriers, the ratio of powders, gas flow, etc. have a significant effect on the microscopic morphology of silicon nitride nanomaterials. Silicon nitride nanomaterials have different microscopic morphologies, different pore structures and pore levels, and different heat conduction paths, the intensity of molecular thermal vibrations, and the degree of barrier during heat transfer, so they have different thermal insulation properties. Therefore, how to design and optimize the structure of silicon nitride nanomaterials is worthy of further study to improve the thermal insulation properties of silicon nitride nanomaterials.

[0003] Reference 1 "Fire-resistant and hydrophobic paper based on Si3N4@PDMS core-shell nanowires with 3D interlocking structure" reported that fire-resistant paper with silicon nitride and polymethylhydrogensiloxane core-shell structure was obtained by heat treatment and curing. The results showed that the fire-resistant paper still maintained mechanical stability after being heated by an alcohol lamp for 30 minutes.

[0004] Reference 2 “Thermally insulating flexible ceramic film based on nanowire-nanosheet dual component synergistic structure with high temperature resistance at 1300°C” reports a refractory paper with a calcium phosphate ceramic-wrapped silicon nitride nanowire structure prepared by high temperature heat treatment, chemical vapor deposition, and electrophoretic pulse deposition. The results show that the refractory paper still maintains mechanical stability after being ignited by a 600°C alcohol lamp for 30 minutes.

[0005] Document 3 "A waterproof and fire-resistant two-component nanowire / nanosheet wound structure paper and its preparation method and application" reports a two-component nanowire / nanosheet wound structure paper. The overall shape of the sample remains unchanged after being burned with an alcohol lamp for 70 minutes.

[0006] Document 4 “A bio-based fire-resistant paper with a fire resistance of 1200 seconds and a preparation method” reports an aerogel paper with a structure of silicon nitride microrods, iron-doped calcium hydrogen phosphate nanobelts and iron-doped calcium hydrogen phosphate particles, which can withstand an alcohol lamp for 1200 seconds without burning and without structural changes.

[0007] The above-mentioned documents obtained silicon nitride nanomaterials with different microscopic morphologies by changing the material system and preparation method. However, the aerogel paper in the above-mentioned documents maintained structural stability when burned in a 600°C alcohol lamp for 70 minutes. When the time exceeded 70 minutes, the material was damaged to varying degrees, which affected the service life of the aerogel paper material. Summary of the invention

[0008] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a silicon nitride micron flower-nanowire double-layer composite insulating aerogel paper and a one-step preparation method thereof, so as to solve the technical problem that the existing silicon nitride nanomaterials are easily damaged after long-term (more than 70 minutes) combustion at 600°C, thereby affecting the service life of the material.

[0009] In order to achieve the above object, the present invention adopts the following technical solutions: The present invention provides a silicon nitride micron flower-nanowire double-layer composite thermal insulation aerogel paper, comprising silicon nitride micron flowers and silicon nitride nanowires; the silicon nitride micron flowers grow on the surface of the silicon nitride nanowires close to the airflow scouring side; in three-dimensional space, the silicon nitride nanowires cross-interlock with each other, and the silicon nitride micron flowers and the silicon nitride nanowires are interlocked.

[0010] In one embodiment, the silicon nitride nanowires have a smooth surface and are cross-distributed in three-dimensional space.

[0011] In one embodiment, the silicon nitride micro-flowers are formed at the locations where the silicon nitride nanowires are entangled or agglomerated, and grow along the direction of airflow.

[0012] In one embodiment, the silicon nitride micro-flower is composed of a plurality of silicon nitride micro-wires, and the diameter of a single silicon nitride micro-wire is 1±0.002 µm.

[0013] In one embodiment, the pore scale of the multi-layered silicon nitride micro-flower-nanowire double-layer composite thermal insulation aerogel paper includes nanometer scale, micrometer scale and millimeter scale; The number of layers of the multi-layered silicon nitride micro-flower-nanowire double-layer composite thermal insulation aerogel paper is no less than 2 layers.

[0014] In one embodiment, the fire resistance time of the multi-layered silicon nitride micro-flower-nanowire double-layer composite thermal insulation aerogel paper at 600° C. is not less than 90 minutes.

[0015] The present invention also provides a one-step preparation method of the silicon nitride micro-flower-nanowire double-layer composite thermal insulation aerogel paper as described above, comprising the following steps: uniformly mixing polysilazane, xylene and ferrocene to prepare a mixed solution; The mixed solution is dried and ground into powder. The powder is granulated into powder with a surface density of 0.6~1kg / m 2 After evenly laying, The powder was heat treated under a nitrogen super-strong airflow at a flow rate of 1200ml / min~1800ml / min to produce a silicon nitride micro-flower-nanowire double-layer composite thermal insulation aerogel paper in one step.

[0016] In one embodiment, the mass ratio of the polysilazane to xylene is 3:2 to 2:1.

[0017] In one embodiment, the mass ratio of ferrocene to polysilazane is 1:9 to 1:11.

[0018] In one embodiment, the drying time is 7-14 days.

[0019] In one embodiment, the heat treatment process is as follows: heating to 1400-1480° C., keeping the temperature for 4-5 hours, and then cooling to room temperature.

[0020] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a silicon nitride micron flower-nanowire double-layer composite heat-insulating aerogel paper, wherein silicon nitride micron flowers are introduced on the surface of silicon nitride nanowires to optimize the structure of silicon nitride nanowire aerogel paper, thereby improving the fire-resistant heat-insulating performance of silicon nitride nanomaterials under a 600°C alcohol lamp. The presence of silicon nitride micron flowers on the surface of silicon nitride nanowires increases the pore size of silicon nitride nanomaterials in actual laminated use from nanometer-micrometer level to nanometer-micrometer-millimeter level, silicon nitride nanowires are cross-distributed in three-dimensional space, and silicon nitride micron flowers are formed at the entanglement or agglomeration of silicon nitride nanowires. The interlocking between nanowires and between micron flowers and nanowires prolongs the path of solid heat conduction in the heat transfer process, and at the same time, the frequency of thermal vibration of air phonons increases, which hinders the heat transfer process, thereby improving the fire-resistant heat-insulating performance of silicon nitride aerogel paper.

[0021] The present invention provides a one-step preparation method of silicon nitride micron flower-nanowire double-layer composite thermal insulation aerogel paper, which uses a large number of reaction raw materials, and under the strong airflow, many silicon nitride micron wires with a diameter of about 1 µm are formed and burst out along the airflow direction at the agglomeration of the bottom silicon nitride nanowires to form a micron flower structure, thereby preparing silicon nitride micron flower-nanowire double-layer composite thermal insulation aerogel paper. It is precisely because of the synergistic optimization effect of "micron flowers" and "nanowires" in the silicon nitride micron flower-nanowire double-layer composite thermal insulation aerogel paper prepared in one step that the thermal insulation effect of silicon nitride aerogel paper is significantly improved during actual lamination use, and it still maintains mechanical stability and no change in microscopic morphology when baked under the flame of a 600°C alcohol lamp for 90 minutes, which is 28.5% higher than that in the literature. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a scanning electron microscope photograph of the silicon nitride micro-flower-nanowire double-layer composite thermal insulation aerogel paper prepared in one step in Example 1.

[0023] Figure 2 This is a scanning electron microscope photograph of the silicon nitride micro-flower-nanowire double-layer composite thermal insulation aerogel paper prepared in one step in Example 1.

[0024] Figure 3 This is a scanning electron microscope photograph of the silicon nitride micro-flower-nanowire double-layer composite thermal insulation aerogel paper prepared in one step in Example 1.

[0025] Figure 4 This is a scanning electron microscope photograph of the bursting point of the upper layer of micro-flowers at the agglomeration of the bottom layer of nano-wires of the silicon nitride micro-flower-nanowire double-layer composite insulation aerogel paper prepared in one step in Example 1.

[0026] Figure 5 This is a scanning electron microscope photograph of the silicon nitride nanowires at the bottom layer of the silicon nitride micro-flower-nanowire double-layer composite thermal insulation aerogel paper prepared in one step in Example 1.

[0027] Figure 6 These are optical photographs and thickness measurement photographs of the silicon nitride micro-flower-nanowire double-layer composite thermal insulation aerogel paper prepared in one step in Example 1.

[0028] Figure 7 This is a graph showing the flame resistance test results of a 600°C alcohol lamp when two layers of silicon nitride micro-flower-nanowire double-layer composite thermal insulation aerogel paper prepared in one step in Example 1 are stacked and used.

[0029] Figure 8This is an infrared photograph of the temperature on the back side of the double-layer aerogel paper of silicon nitride micro-flower-nanowire composite heat-insulating aerogel paper prepared in one step in Example 1 when the two layers are stacked and used under the ignition of an alcohol lamp.

[0030] Fig. 9 This is a surface optical photograph of the silicon nitride micro-flower-nanowire double-layer composite thermal insulation aerogel paper prepared in one step in Example 1 after being tested with a 600°C alcohol lamp.

[0031] Fig.10 This is the weight of the silicon nitride micro-flower-nanowire double-layer composite thermal insulation aerogel paper prepared in one step in Example 1 before and after the 600°C alcohol lamp test.

[0032] Fig.11 It is a schematic diagram of the design of an integrated graphite box for carrying powder.

[0033] Fig.12 This is a microstructure photograph of the silicon nitride aerogel paper having only nanowire morphology, which was prepared in Comparative Example 1 under the condition of insufficient powder.

[0034] Fig.13 This is a microstructure photograph of the silicon nitride aerogel paper having only nanowire morphology prepared in comparative example 2 under the condition of insufficient gas flow. DETAILED DESCRIPTION

[0035] In order to enable those skilled in the art to understand the characteristics and effects of the present invention, the following is a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used in the text are the common meanings understood by those skilled in the art for the present invention. In the event of a conflict, the definition in this specification shall prevail.

[0036] The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, that is, the present invention can be implemented without being limited by any specific theory or mechanism.

[0037] In this article, all features such as values, quantities, contents and concentrations defined in the form of numerical ranges or percentage ranges are for simplicity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to have included and specifically disclosed all possible secondary ranges and individual values ​​within the range (including integers and fractions).

[0038] In this document, unless otherwise specified, “includes,” “including,” “contains,” “has,” or similar terms cover the meanings of “consisting of” and “mainly consisting of,” for example, “A includes a” covers the meanings of “A includes a and other” and “A only includes a.”

[0039] In this document, in order to make the description concise, not all possible combinations of various technical features in various embodiments or examples are described. Therefore, as long as there is no contradiction in the combination of these technical features, the various technical features in various embodiments or examples can be combined arbitrarily, and all possible combinations should be considered to be within the scope of this specification.

[0040] The present invention provides a silicon nitride micron flower-nanowire double-layer composite thermal insulation aerogel paper. In the silicon nitride micron flower-nanowire double-layer composite thermal insulation aerogel paper, silicon nitride micron wires are formed at places where silicon nitride nanowires are more agglomerated, and burst out and grow along the airflow direction under the scouring of strong airflow, and silicon nitride micron flowers are formed on the surface of the silicon nitride nanowires. During the actual lamination use process, the silicon nitride micron flower-nanowire double-layer composite thermal insulation aerogel paper with the above structure has its pore scale increased from nanometer-micrometer level to nanometer-micrometer-millimeter level, and the phonon thermal vibration of air in the heat transfer process is increased. The interlocking between the silicon nitride micron flower and the silicon nitride nanowire can extend the path of solid heat conduction in the heat transfer process, consume energy, hinder heat transfer, and make it have good fire-resistant thermal insulation performance.

[0041] The present invention also provides a method for preparing a silicon nitride micro-flower-nanowire double-layer composite thermal insulation aerogel paper in one step, comprising the following steps: (1) uniformly mixing polysilazane, xylene and ferrocene, wherein the mass ratio of polysilazane to xylene is 3:2-2:1, and the mass ratio of ferrocene to polysilazane is 1:9-1:11, and ultrasonicating for 3-5 hours to obtain a mixed solution.

[0042] (2) The mixed solution prepared in step (1) is air-dried for 7-14 days and then ground into powder using a mortar.

[0043] (3) Make a Fig.11 The one-piece closed graphite box shown in the figure is used to grind the powder in step (2) to a surface density of 0.6~1.0kg / m 2 Lay evenly in the graphite box.

[0044] (4) The graphite box is placed in a box-type atmosphere furnace, and nitrogen is introduced at a flow rate of 1200 ml / min~1800 ml / min. The box is heated to 1400~1480°C and kept at this temperature for 4-5 hours under the flushing of nitrogen super-strong airflow, and then cooled in the furnace to obtain a silicon nitride refractory aerogel paper material with a multi-level structure of micron flowers + nanowires in one step.

[0045] The above one-step preparation method uses more powder raw materials (surface density 0.6~1.0 kg / m 2), and under strong airflow (1200ml / min~1800ml / min), a silicon nitride micro-flower-nanowire double-layer composite thermal insulation aerogel paper was prepared in one step, see Figure 6 The thickness of the single-layer aerogel paper is only 0.66mm. Thanks to the presence of silicon nitride micron flowers above the silicon nitride nanowires, the pore size of the silicon nitride nanomaterial in actual stacking is increased from nano-micron level to nano-micron-millimeter level, which intensifies the intensity of the phonon thermal vibration of the air during heat transfer, increases the energy consumption path, hinders the heat transfer, and improves the fire-resistant and heat-insulating properties of the silicon nitride nanomaterial. When ignited by a 600°C alcohol lamp, the fire-resistant and heat-insulating time is increased by 28.5% compared with the background technology.

[0046] For details, see Fig.11 , spread the powder evenly in the yellow area in the graphite box diagram, tie it up and seal it with carbon rope before proceeding to the next step of heat treatment.

[0047] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0048] The following examples use conventional instruments and equipment in the art. The experimental methods in the following examples where specific conditions are not specified are usually carried out under conventional conditions or under conditions recommended by the manufacturer. The various raw materials used in the following examples are conventional commercial products unless otherwise specified, and their specifications are conventional specifications in the art. In the specification of the present invention and the following examples, unless otherwise specified, "%" means weight percentage, "part" means weight part, and ratio means weight ratio.

[0049] Example 1 (1) Polysilazane, xylene and ferrocene are uniformly mixed, wherein the mass ratio of polysilazane to xylene is 3:2, and the mass ratio of ferrocene to polysilazane is 1:9, and ultrasonic treatment is performed for 3 hours to obtain a mixed solution.

[0050] (2) The mixed solution prepared in step (1) was naturally dried for 7 days and ground into powder using a mortar.

[0051] (3) Make an integrated closed graphite box, such as Fig.11 As shown, the powder ground in step (2) is mixed with a surface density of 0.6 kg / m 2 Lay evenly in the graphite box.

[0052] (4) The graphite box is placed in a box-type atmosphere furnace, nitrogen is introduced at a flow rate of 1200 ml / min, and the furnace is heated to 1400°C for 4 hours, followed by cooling in the furnace to obtain a silicon nitride refractory aerogel paper material having a multi-level structure of micron flowers + nanowires in one step.

[0053] In Example 1, a silicon nitride structure of "upper layer micron flowers and lower layer nanowires" was simultaneously prepared on a graphite box substrate. After being baked under an alcohol lamp flame for 90 minutes, the quality of the aerogel paper did not change, and no damage occurred on the burning surface.

[0054] Example 2 (1) Polysilazane, xylene and ferrocene are uniformly mixed, wherein the mass ratio of polysilazane to xylene is 2:1, and the mass ratio of ferrocene to polysilazane is 1:11, and ultrasonic treatment is performed for 5 hours to obtain a mixed solution.

[0055] (2) The mixed solution prepared in step (1) was naturally dried for 14 days and then ground into powder using a mortar.

[0056] (3) Make an integrated closed graphite box, such as Fig.11 As shown, the powder ground in step (2) is mixed with a surface density of 1.0 kg / m 2 Lay evenly in the graphite box.

[0057] (4) The graphite box is placed in a box-type atmosphere furnace, nitrogen is introduced at a flow rate of 1800 ml / min, and the temperature is heated to 1480°C and kept at this temperature for 5 h. The box is then cooled in the furnace to obtain a silicon nitride micro-flower-nanowire double-layer composite thermal insulation aerogel paper in one step.

[0058] In Example 2, a silicon nitride structure of "upper layer micron flowers and lower layer nanowires" was simultaneously prepared on a graphite box substrate. After being baked under an alcohol lamp flame for 85 minutes, the quality of the aerogel paper did not change and no damage was found on the burning surface.

[0059] Example 3 (1) Polysilazane, xylene and ferrocene are uniformly mixed, wherein the mass ratio of polysilazane to xylene is 7:4, and the mass ratio of ferrocene to polysilazane is 1:10, and ultrasonic treatment is performed for 4 hours to obtain a mixed solution.

[0060] (2) The mixed solution prepared in step (1) was naturally dried for 10 days and then ground into powder using a mortar.

[0061] (3) Make an integrated closed graphite box, such as Fig.11 As shown, the powder ground in step (2) is mixed with a surface density of 0.8 kg / m 2 Lay evenly in the graphite box.

[0062] (4) The graphite box was placed in a box-type atmosphere furnace, nitrogen was introduced at a flow rate of 1600 ml / min, and the temperature was heated to 1450°C for 4.5 h. The box was then naturally cooled to obtain a silicon nitride aerogel paper material with "upper layer micron flowers and lower layer nanowires".

[0063] In Example 3, a double-layer composite thermal insulation aerogel paper of silicon nitride micro-flowers and nanowires was prepared on a graphite box substrate. After being baked under an alcohol lamp flame for 80 minutes, the quality of the aerogel paper did not change, and no obvious damage was observed on the burning surface.

[0064] Example 4 (1) Polysilazane, xylene and ferrocene are uniformly mixed, wherein the mass ratio of polysilazane to xylene is 8:5, and the mass ratio of ferrocene to polysilazane is 1:9, and a mixed solution is obtained after ultrasonic treatment for 3.5 hours.

[0065] (2) The mixed solution prepared in step (1) was naturally dried for 12 days and then ground into powder using a mortar.

[0066] (3) Make an integrated closed graphite box, such as Fig.11 As shown, the powder ground in step (2) is mixed with a surface density of 0.7 kg / m 2 Lay evenly in the graphite box.

[0067] (4) The graphite box is placed in a box-type atmosphere furnace, nitrogen is introduced at a flow rate of 1300 ml / min, and the furnace is heated to 1470°C for 4 hours. The furnace is then cooled to obtain a silicon nitride refractory aerogel paper material with a multi-level structure of micron flowers + nanowires in one step.

[0068] In Example 4, a double-layer composite thermal insulation aerogel paper of silicon nitride micro-flowers and nanowires was prepared on a graphite box substrate. After being baked under an alcohol lamp flame for 90 minutes, the quality of the aerogel paper did not change, and no obvious damage was found on the burning surface.

[0069] Comparative Example 1 (1) Polysilazane, xylene and ferrocene are uniformly mixed, wherein the mass ratio of polysilazane to xylene is 3:2, and the mass ratio of ferrocene to polysilazane is 1:9, and a mixed solution is obtained after ultrasonic treatment for 3.5 hours.

[0070] (2) The mixed solution prepared in step (1) was naturally dried for 12 days and then ground into powder using a mortar.

[0071] (3) Make an integrated closed graphite box, such as Fig.11 As shown, the powder ground in step (2) is mixed with a surface density of 0.15 kg / m 2 Lay evenly in the graphite box.

[0072] (4) The graphite box was placed in a box-type atmosphere furnace, nitrogen was introduced at a flow rate of 1600 ml / min, heated to 1470°C and kept warm for 3 h, and then cooled in the furnace to obtain only silicon nitride nanowire aerogel paper with a three-dimensional overlapping nanowire morphology.

[0073] See also Fig.12 , Comparative Example 1 has less powder (0.015g / cm 2 ), under high gas flow conditions, silicon nitride nanowire aerogel paper with only nanowire morphology was prepared, and there was no silicon nitride nanomaterial with microflower morphology composed of microwires.

[0074] Comparative Example 2 (1) Polysilazane, xylene and ferrocene are uniformly mixed, wherein the mass ratio of polysilazane to xylene is 7:4, and the mass ratio of ferrocene to polysilazane is 1:10, and a mixed solution is obtained after ultrasonic treatment for 4 hours.

[0075] (2) The mixed solution prepared in step (1) was naturally dried for 10 days and then ground into powder using a mortar.

[0076] (3) Make an integrated closed graphite box, such as Fig.11 As shown, the powder ground in step (2) is mixed with a surface density of 0.8 kg / m 2 Lay evenly in the graphite box.

[0077] (4) The graphite box was placed in a box-type atmosphere furnace, nitrogen was introduced at a flow rate of 60 ml / min, and the temperature was heated to 1450°C and kept at that temperature for 4.5 h. The furnace was then cooled, and only silicon nitride nanowire aerogel paper with a three-dimensional overlapping nanowire morphology was obtained.

[0078] See also Fig.13 In comparative example 2, with more powder and lower gas flow rate (60 ml / min), silicon nitride nanowire aerogel paper with only nanowire morphology was prepared, and there was no silicon nitride nanomaterial with micron flower morphology composed of micron wires.

[0079] See also Figure 1 , it can be seen that there are a large number of silicon nitride micro-flowers distributed on the surface of silicon nitride nanowires. Specifically, silicon nitride micro-flowers grow on the surface of silicon nitride nanowires close to the side of the airflow. In three-dimensional space, silicon nitride nanowires interlock with each other, and silicon nitride micro-flowers and silicon nitride nanowires interlock. Figure 2 and Figure 3 It can be seen that the micron flowers are distributed along the airflow direction, and the size of a single silicon nitride micron flower is 1.002µm. Figure 4 As shown in FIG, the silicon nitride micro-flower is composed of a plurality of silicon nitride micro-wires, and the micro-wires grow silicon nitride micro-flowers at the aggregation of the underlying nanowires under the action of a catalyst. Figure 5It can be seen that the surface of silicon nitride nanowires is smooth and cross-distributed in three-dimensional space.

[0080] In order to verify the excellent fire-resistant and heat-insulating performance of the silicon nitride micro-flower-nanowire double-layer composite thermal insulation aerogel paper prepared in one step in actual lamination use, a 600°C alcohol lamp flame combustion test was carried out on Example 1, Example 2, Example 3 and Example 4. The experimental results are shown in FIG. Figure 7 , Figure 8 and Fig. 9 , Fig.10 As shown, after the silicon nitride micro-flower-nanowire double-layer composite insulation aerogel paper prepared in one step was burned in a 600°C alcohol lamp for 90 minutes, the film quality did not change, and there was no obvious damage on the burning surface. The aerogel paper still maintained mechanical stability, and the fire resistance time was 28.5% higher than the highest fire resistance time mentioned in the literature, proving that the silicon nitride micro-flower-nanowire double-layer composite insulation aerogel paper prepared in one step has excellent fire resistance.

[0081] Based on the above experimental results, the pore scales of the multi-layered silicon nitride micron flower-nanowire double-layer composite thermal insulation aerogel paper include nanometer, micron and millimeter levels; the number of layers of the multi-layered silicon nitride micron flower-nanowire double-layer composite thermal insulation aerogel paper is not less than 2 layers, and the fire resistance time of the multi-layered silicon nitride micron flower-nanowire double-layer composite thermal insulation aerogel paper at 600°C is not less than 90 minutes. And the fire resistance time increases with the number of superimposed layers of the silicon nitride micron flower-nanowire double-layer composite thermal insulation aerogel paper.

[0082] Combined with Fig.12 and Fig.13 , referring to the results of Example 1 and Comparative Example 1, Example 2 and Comparative Example 2, it can be proved that if the two reaction conditions of more powder and higher gas flow rate are not met at the same time, only silicon nitride nanomaterials with nanowire morphology can be obtained, and the silicon nitride micron flower-nanowire double-layer composite insulating aerogel paper cannot be prepared in one step.

[0083] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A silicon nitride micron flower-nanowire double-layer composite thermal insulation aerogel paper, characterized in that: It includes silicon nitride micro-flowers and silicon nitride nanowires; the silicon nitride micro-flowers grow on the surface of the silicon nitride nanowires close to the airflow scouring side; in three-dimensional space, the silicon nitride nanowires cross and interlock with each other, and the silicon nitride micro-flowers and silicon nitride nanowires interlock.

2. The silicon nitride micro-flower-nanowire double-layer composite thermal insulation aerogel paper according to claim 1, characterized in that: The silicon nitride micro-flowers are formed at the places where the silicon nitride nanowires are entangled or agglomerated, and grow along the direction of air flow.

3. The silicon nitride micro-flower-nanowire double-layer composite thermal insulation aerogel paper according to claim 1, characterized in that: The silicon nitride micron flower is composed of a plurality of silicon nitride micron wires.

4. The silicon nitride micro-flower-nanowire double-layer composite thermal insulation aerogel paper according to claim 3, characterized in that: The diameter of a single silicon nitride microwire is 1±0.002 µm.

5. The silicon nitride micro-flower-nanowire double-layer composite thermal insulation aerogel paper according to claim 1, characterized in that: The pore scales of the multi-layered silicon nitride micro-flower-nanowire double-layer composite thermal insulation aerogel paper include nanometer, micrometer and millimeter levels; The number of layers of the multi-layered silicon nitride micro-flower-nanowire double-layer composite thermal insulation aerogel paper is no less than 2 layers.

6. The silicon nitride micro-flower-nanowire double-layer composite thermal insulation aerogel paper according to claim 5, characterized in that: The fire-resistant time of the multi-layered silicon nitride micro-flower-nanowire double-layer composite thermal insulation aerogel paper at 600° C. is not less than 90 minutes.

7. A one-step preparation method of the silicon nitride micro-flower-nanowire double-layer composite thermal insulation aerogel paper as claimed in any one of claims 1 to 6, characterized in that: The following steps are involved: uniformly mixing polysilazane, xylene and ferrocene to prepare a mixed solution; The mixed solution is dried and ground into powder. The powder is granulated into powder with a surface density of 0.6~1kg / m 2 After evenly laying, The powder was heat treated under a nitrogen super-strong airflow at a flow rate of 1200ml / min~1800ml / min to produce a silicon nitride micro-flower-nanowire double-layer composite thermal insulation aerogel paper in one step.

8. The one-step preparation method of silicon nitride micro-flower-nanowire double-layer composite thermal insulation aerogel paper according to claim 7, characterized in that: The mass ratio of the polysilazane to xylene is 3:2-2:1; the mass ratio of the ferrocene to polysilazane is 1:9-1:

11.

9. The one-step preparation method of silicon nitride micro-flower-nanowire double-layer composite thermal insulation aerogel paper according to claim 7, characterized in that: The drying time is 7-14 days.

10. The one-step preparation method of silicon nitride micro-flower-nanowire double-layer composite thermal insulation aerogel paper according to claim 7, characterized in that: The heat treatment process is as follows: Heat to 1400-1480℃, keep warm for 4-5h, and then cool to room temperature.

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